High accuracy emplacement of fragile electronic sensor payloads for ground or sea monitoring is typically addressed utilizing either free fall or parachute-deployed systems. Unfortunately, both of these approaches have serious drawbacks relating to accuracy in the case of the parachute delivery approach and high impact loads in the case of the free fall technique. Furthermore, while it is possible to address specific environmental constraints such as winds aloft under certain conditions, both of the existing systems suffer from accuracy susceptibility due to limited control authority or lack of apriori information. Finally, in the case of the parachute system, two additional drawbacks are hang time, which optically exposes the payload and delivery vehicle to unwanted scrutiny for long periods of time, and the physical size of the deployment mechanism required to ensure emplacement of the payload. Additional post deployment issues with observability of a large parachute canopy further spoil observability.
A need, therefore, exists for an improved way of emplacing sensitive electronics without risking damage due to shock loads associated with impact and the need for a covert, autonomous, emplacement capability in the presence of strong external factors, such as environmental constraints, with extremely high accuracy, as well as post emplacement preservation of covert aspects of sensor operation.
More particularly, the problem in covertly emplacing relatively fragile sensors is the ability to air launch the sensors, have a controlled descent to limit their downward velocity and have them placed at a precise geophysical location which has been pre-targeted. It is important that the sensitive payload not impact the ground. This requirement for a soft landing eliminates the possibility of standard parachute deployment where the payload impacts the ground at some unknown velocity against some unknown surface where damage to the payload can occur.
It is noted that the payloads envisioned are very sensitive sensors, often employing sensitive imaging cameras or radars, which are subject to damage during parachuting or dead-dropping.
The problem with dead-dropping of payloads is also that the accuracies involved are minimal. If one does not know where the payload is going to land within a mile of the target due to winds aloft, then precision emplacement is impossible.
Note that when a payload is dropped using a parachute it hits with some terminal velocity that is not necessarily controlled and does not necessarily result in the payload landing right side up. Note also that whatever the terminal velocity is, it can damage relatively fragile sensors so that if a rock is hit at high speed there is a substantial risk of damaging the sensitive radar, optical device or other sensor.
Moreover, it is important to be able to deploy payloads as high as 40,000 or as low as 40 feet. There is therefore a necessity to provide a payload velocity limiting system that can deploy quickly from the payload over a wide range of altitudes. For instance, one needs to have enough altitude to perform a precision drop and have the payload emplaced exactly on a predetermined spot. Moreover, there needs to be enough altitude to be able to determine the geophysical location of the payload, having preloaded the target's location, and to be able to solve the guidance problem to develop an optimum trajectory for the payload to travel in order to be precisely emplaced.
Additionally, for low or minimum altitudes one needs to provide almost instantaneous deceleration of the payload and almost instantaneous trajectory control. For higher altitudes, one may wish to delay deployment of the decelerating device to let the payload freefall in the general vicinity of the target location until it gets to a so-called deployment basket where one can deploy deceleration and activate guidance. At the point that the deceleration mechanism is deployed it would be desirable to instantly calculate the optimum trajectory to route the payload to the target.
Moreover, when the payload is sufficiently close to the landing point it would be desirable to brake the descent of the payload, and to level the payload so as to protect the sensitive sensors and to provide for optimal sensor orientation.
Thus, it is important to provide payload descents which provide for a soft landing and to provide for the ability to adjust the sensor when landing on an uneven, rocky terrain.
In summary, it is important to provide a sensor delivery system which is covert and has an acoustically low signature as well as a low radar cross section, and that is faster than using a parachute and considerably more controllable than a parachute so that the payload is gently delivered to the exact target spot in the ground, the minimal observability, both in flight and post landing, by limiting the time that the payload descents, with a brake provided to limit impact velocity.